U.S. patent number 11,146,436 [Application Number 16/616,857] was granted by the patent office on 2021-10-12 for terminal apparatus and base station apparatus.
This patent grant is currently assigned to FG Innovation Company Limited, SHARP KABUSHIKI KAISHA. The grantee listed for this patent is FG INNOVATION COMPANY LIMITED, SHARP KABUSHIKI KAISHA. Invention is credited to Jungo Goto, Yasuhiro Hamaguchi, Osamu Nakamura, Takashi Yoshimoto.
United States Patent |
11,146,436 |
Nakamura , et al. |
October 12, 2021 |
Terminal apparatus and base station apparatus
Abstract
Proper use of a sparse code prevents PAPR performance from
improperly degrading.
Inventors: |
Nakamura; Osamu (Sakai,
JP), Yoshimoto; Takashi (Sakai, JP), Goto;
Jungo (Sakai, JP), Hamaguchi; Yasuhiro (Sakai,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
SHARP KABUSHIKI KAISHA
FG INNOVATION COMPANY LIMITED |
Sakai
Tuen Mun |
N/A
N/A |
JP
HK |
|
|
Assignee: |
SHARP KABUSHIKI KAISHA (Sakai,
JP)
FG Innovation Company Limited (Tuen Mun, HK)
|
Family
ID: |
1000005861997 |
Appl.
No.: |
16/616,857 |
Filed: |
May 30, 2018 |
PCT
Filed: |
May 30, 2018 |
PCT No.: |
PCT/JP2018/020646 |
371(c)(1),(2),(4) Date: |
November 25, 2019 |
PCT
Pub. No.: |
WO2018/221549 |
PCT
Pub. Date: |
December 06, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210135920 A1 |
May 6, 2021 |
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Foreign Application Priority Data
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May 31, 2017 [JP] |
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JP2017-107943 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
5/0044 (20130101); H04L 27/2605 (20130101); H04L
27/2615 (20130101) |
Current International
Class: |
H04L
27/26 (20060101); H04L 5/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3295635 |
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Sep 2019 |
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EP |
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WO-2016159464 |
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Oct 2016 |
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WO |
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WO-2018027589 |
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Feb 2018 |
|
WO |
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WO-2018028123 |
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Feb 2018 |
|
WO |
|
Other References
"Study on provision of low-cost Machine-Type Communications (MTC)
User Equipments (UEs) based on LTE", 3GPP TR36.888 V12.0.0, Jun.
2013. cited by applicant .
"Cellular system support for ultra-low complexity and low
throughput Internet of Things (CIoT)", 3GPP TR45.820 V13.0.0, Aug.
2015. cited by applicant .
Huawei et al., "Sparse Code Multiple Access (SCMA) for 5G radio
transmission", R1-162155, 3GPP TSG RAN WG1 Meeting #84bis Busan,
Korea, Apr. 11-15, 2016. cited by applicant.
|
Primary Examiner: Patel; Jay P
Attorney, Agent or Firm: ScienBiziP, P.C.
Claims
The invention claimed is:
1. A terminal apparatus that transmits a data signal to a base
station apparatus, the terminal apparatus comprising: a
transmission parameter configuration unit configured to generate a
sequence including a zero and to transmit the data signal; a spread
unit configured to multiply a modulation symbol of the data signal
by the sequence; and a mapping unit configured to map the data
signal multiplied by the sequence to a first radio resource area or
a second radio resource area each including multiple resource
elements, wherein the transmission parameter configuration unit
causes the sequence by which the modulation symbol mapped to the
first radio resource area is multiplied and the sequence by which
the modulation symbol mapped to the second radio resource area is
multiplied to be differently configured depending on whether the
transmission of the data signal is an initial transmission or a
retransmission.
2. The terminal apparatus according to claim 1, wherein the first
radio resource area is included in a first orthogonal frequency
division multiplexing (OFDM) symbol, the second radio resource area
is included in a second OFDM symbol, and a subcarrier for a
resource element of the multiple resource elements in the first
radio resource area overlaps with a subcarrier for a resource
element of the multiple resource elements in the second radio
resource area.
3. The terminal apparatus according to claim 2, wherein the
transmission parameter configuration unit generates the sequence
such that a number of the multiple resource elements included in
the first OFDM symbol is identical to a number of the multiple
resource elements included in the second OFDM symbol.
4. The terminal apparatus according to claim 1, wherein the first
radio resource area is included in a first subcarrier, the second
radio resource area is included in a second subcarrier, and an OFDM
symbol for a resource element of the multiple resource elements in
the first radio resource area overlaps with an OFDM symbol for a
resource element of the multiple resource elements in the second
radio resource area.
5. The terminal apparatus according to claim 4, wherein the
multiple resource elements in the first radio resource area and the
multiple resource elements in the second radio resource area each
includes a first OFDM symbol and a second OFDM symbol, and the
transmission parameter configuration unit generates the sequence
such that a number of the multiple resource elements included in
the first OFDM symbol is identical to a number of the multiple
resource elements included in the second OFDM symbol.
Description
TECHNICAL FIELD
The present invention relates to a transmission apparatus and a
reception apparatus.
This application claims priority based on JP 2017-107943 filed on
May 31, 2017, the contents of which are incorporated herein by
reference.
BACKGROUND ART
In recent years, 5th Generation mobile communication systems have
been standardized, where a goal is to achieve MTC by a large number
of terminal apparatuses (massive machine type communications:
mMTC), ultra-reliable and low latency communications (URLLC), and
large-capacity, high-speed communications (enhanced mobile
broadband: eMBB). Especially, Internet of Things (IoT) is expected
to be achieved by using various types of apparatuses in the future,
and achieving the mMTC has been one of important factors in 5G.
For example, in 3rd Generation Partnership Project (3GPP), a
Machine-to-Machine (M2M) communication technology has been
standardized as a Machine Type Communication (MTC) that
accommodates a terminal apparatus that transmits and/or receives
small size data (NPL 1). Furthermore, in order to support data
transmission at a low rate in a narrow band, standardization of
Narrow Band-IoT (NB-IoT) has been conducted (NPL 2).
In Long Term Evolution (LTE), LTE-Advanced, LTE-Advanced Pro, and
the like that have been standardized in the 3GPP, a terminal
apparatus transmits a Scheduling Request (SR) in a case that a
traffic of transmission data occurs, and after the terminal
apparatus receives control information of an uplink transmission
grant (UL Grant) from a base station apparatus, the terminal
apparatus transmits data with transmission parameters of the
control information included in the UL Grant at a predetermined
timing. In this manner, a radio communication technology is
achieved that allows the base station apparatus to perform radio
resource control for all uplink data transmissions (data
transmissions from the terminal apparatus to the base station
apparatus). Accordingly, the base station apparatus can achieve an
Orthogonal Multiple Access (OMA) by controlling the radio resources
and can receive uplink data by simple reception processing.
Meanwhile, in such a conventional radio communication technology,
in order for the base station apparatus to perform all radio
resource controls, the control information need to be transmitted
and/or received before the data transmission regardless of amount
of data to be transmitted by the terminal apparatus. Especially, in
a case that the size of the data to be transmitted is small, the
control information accounts for a relatively high proportion.
Thus, in a case that a terminal performs a transmission of data
with a small size, a contention-based (grant-free) radio
communication technology in which the terminal apparatus performs a
SR transmission and a data transmission without receiving the UL
Grant transmitted by the base station apparatus, is effective in
terms of an overhead taken by the control information. Furthermore,
in the contention-based radio communication technology, a time
taken from data generation to data transmission may be
shortened.
In the contention-based radio communications, since the UL Grant is
absent, a large number of terminal apparatuses may use the same
radio resources. In other words, a large number of signals collide
with one another and are received by a receive antenna of the base
station apparatus. A reception apparatus in the base station
apparatus needs to detect signals from the respective terminal
apparatuses, and Sparse Code Multiple Access (SCMA) has been
proposed as one of methods to address such a need. In the SCMA,
data is spread to multiple subcarriers by using a code book
including zeros (sparse code) and transmitted, with the assumption
of an access method, such as an OFDM, that has multiple
subcarriers. The use of a message passing algorithm (MPA) allows a
receiver to detect a signal with a small amount of computation (NPL
3).
CITATION LIST
Non Patent Literature
NPL 1: 3GPP, TR36.888 V12.0.0, "Study on provision of low-cost
Machine-Type Communications (MTC) User Equipments (UEs) based on
LTE," June 2013 NPL 2: 3GPP, TR45.820 V13.0.0, "Cellular system
support for ultra-low complexity and low throughput Internet of
Things (CIoT)," August 2015 NPL 3: Huawei, HiSilicon, "Sparse Code
Multiple Access (SCMA) for 5G radio transmission", R1-162155,
Busan, Korea, Apr. 11-15, 2016
SUMMARY OF INVENTION
Technical Problem
The SCMA performs spreading by using sparse code, and a
Peak-to-Average Power Ratio (PAPR) significantly varies depending
on which sparse code is used. As for the sparse code, while the use
of the sparse code in a frequency direction has been proposed, the
use of the sparse code in a time direction can also be considered
taking into account a frequency fluctuation due to fading. At this
time, there is a case where powers of multiple OFDM symbols become
zeros. In a case that the power of a certain OFDM symbol becomes
zero, an average transmit power of an entire frame (or subframe or
slot) decreases, and therefore the PAPR increases. The degradation
of the PAPR is not preferable because it leads to a load on a power
amplifier, considering a terminal apparatus, in particular, a
sensor assumed in the mMTC or the like.
One aspect of the present invention has been made in view of the
foregoing, and there is provided a technology for preventing the
degradation of the PAPR in an access method using the sparse code
such the SCMA.
Solution to Problem
(1) One aspect of the present invention has been made to solve the
above-described problems, and one aspect of the present invention
is a terminal apparatus that transmits a data signal to a base
station apparatus. The terminal apparatus includes a transmission
parameter configuration unit, a spread unit, and a mapping unit.
The transmission parameter configuration unit is configured to
generate a sequence including a zero. The spread unit is configured
to multiply a modulation symbol of the data signal by the sequence.
The mapping unit is configured to map the signal multiplied by the
sequence to a first radio resource area or a second radio resource
area including multiple resource elements. The transmission
parameter configuration unit cause the sequence by which the
modulation symbol mapped to the first radio resource area is
multiplied and the sequence by which the modulation symbol mapped
to the second radio resource area is multiplied to be differently
configured.
(2) In addition, according to one aspect of the present invention,
the first radio resource area is included in a first OFDM symbol.
The second radio resource area is included in a second OFDM symbol.
A subcarrier for a resource element of the multiple resource
elements in the first radio resource area overlaps with a
subcarrier for a resource element of the multiple resource elements
in the second radio resource area.
(3) In addition, according to one aspect of the present invention,
the transmission parameter configuration unit configures the
sequence such that the number of the multiple resource elements
included in the first OFDM symbol becomes identical to the number
of the multiple resource elements included in the second OFDM
symbol.
(4) In addition, according to one aspect of the present invention,
the first radio resource area is included in a first subcarrier,
the second radio resource area is included in a second subcarrier.
An OFDM symbol for a resource element of the multiple resource
elements in the first radio resource area overlaps with an OFDM
symbol for a resource element of the multiple resource elements in
the second radio resource area.
(5) In addition, according to one aspect of the present invention,
the multiple resource elements in the first radio resource area and
the multiple resource elements in the second radio resource area
include a first OFDM symbol and a second OFDM symbol. The
transmission parameter configuration unit configures the sequences
such that the number of the multiple resource elements included in
the first OFDM symbol becomes identical to the number of the
multiple resource elements included in the second OFDM symbol.
(6) In addition, according to one aspect of the present invention,
the transmission parameter configuration unit causes the sequence
by which the modulation symbol mapped to the first radio resource
area is multiplied and the sequence by which the modulation symbol
mapped to the second radio resource area is multiplied to be
differently configured depending on whether transmission is an
initial transmission or a retransmission.
Advantageous Effects of Invention
According to the aspects of the present invention, a reduction in a
PAPR can be achieved in an access method, such as SCMA, that uses a
sparse code.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagram illustrating an example of a system
configuration according to the present embodiment.
FIG. 2 is a diagram illustrating a configuration example of a
transmitter in a terminal apparatus according to the present
embodiment.
FIG. 3 is a diagram illustrating a resource allocation in a case
that a fixed sparse code is applied to a frequency domain according
to the present embodiment.
FIG. 4 is a diagram illustrating a resource allocation in a case
that a variable sparse code is applied to the frequency domain
according to the present embodiment.
FIG. 5 is a diagram illustrating a resource allocation in a case
that the fixed sparse code is applied to a time domain according to
the present embodiment.
FIG. 6 is a diagram illustrating a resource allocation in a case
that a different sparse code for each subcarrier is applied to the
time domain according to the present embodiment.
FIG. 7 is a diagram illustrating a resource allocation in a case
that the sparse code is applied such that the number of subcarriers
for each OFDM symbol becomes constant according to the present
embodiment.
FIG. 8 is a diagram illustrating a configuration example of a
receiver in a base station apparatus according to the present
embodiment.
FIG. 9 is a diagram illustrating a resource allocation during
retransmission according to the present embodiment.
FIG. 10 is a diagram illustrating a resource allocation in a case
that a different sparse code for each subcarrier is applied to the
time domain according to the present embodiment.
DESCRIPTION OF EMBODIMENTS
Techniques described herein can be used in various kinds of radio
communication systems, such as a Code Division Multiplexing Access
(CDMA) system, a Time Division Multiplexing Access (TDMA) system, a
Frequency Division Multiplexing Access (FDMA) system, an Orthogonal
FDMA (OFDMA) system, a Single Carrier FDMA (SC-FDMA) system, and
another system. Terms "system" and "network" may often be used
synonymously. A radio technology (standard), such as Universal
Terrestrial Radio Access (UTRA), and cdma2000 (registered
trademark), can be implemented in the CDMA system. The UTRA
includes a broadband CDMA (WCDMA (registered trademark)) and other
modifications of the CDMA. The cdma2000 covers IS-2000, IS-95, and
IS-856 standards. A radio technology, such as a Global System for
Mobile Communications (GSM (registered trademark)) can be
implemented in the TDMA system. A radio technology, such as Evolved
UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi),
IEEE802.16 (WiMAX), IEEE802.20, and a Flash-OFDM (registered
trademark), can be implemented in the OFDMA system. 3GPP Long Term
Evolution (LTE) is an E-UTRA that uses the OFDMA on downlink and
the SC-FDMA on uplink. LTE-A is a system, a radio technology, and a
standard that have improved LTE. The UTRA, E-UTRA, LTE, LTE-A, and
GSM (registered trademark) are described in documents from an
institution named as the Third Generation Partnership Project
(3GPP). The cdma2000 and UMB are described in documents from an
institution named as the 3rd Generation Partnership Project 2
(3GPP2). For clarification, some aspects of the technology are
described below as to data communications in the LTE and the LTE-A,
and terms of the LTE and terms of the LTE-A are often used in the
following description.
Preferable embodiments according to one aspect of the present
invention will be described below in detail with reference to the
accompanying drawings. The detailed description, which is disclosed
in the following together with the accompanying drawings, is to
describe exemplary embodiments of the present invention and is not
intended to describe only one embodiment that allows the present
invention to be embodied. The following detailed description
includes specific details to provide complete understanding of the
present invention. However, it is seen by one skilled in the art
that one aspect of the present invention can be embodied even
without such specific details. For example, while the following
detailed description will be specifically described assuming that
mobile communication systems are 3GPP LTE and LTE-A systems, the
description is also applicable to any other mobile communication
system except for matters specific to the 3GPP LTE and the LTE-A.
Additionally, terms described below are terms defined in
consideration of functions according to one aspect of the present
invention and possibly vary depending on the intent, convention, or
the like of a user and an operator. Accordingly, the terms should
be defined based on content throughout the entire
specification.
In describing the embodiments, a description of technical content
that is well known in a technical field to which one aspect of the
present invention belongs and not directly related to one aspect of
the present invention will be omitted. This is because, by omitting
the unnecessary descriptions, the gist of the present invention is
not obscured and is more clearly conveyed. Accordingly, in some
cases, to avoid concepts of the present invention from being vague,
the known configuration and apparatus can be omitted, or the
description can be illustrated in the form of a block diagram to
focus on key functions of each structure and apparatus. Some
components in the drawings are exaggerated, omitted, or illustrated
schematically such that the gist of the present invention is not
obscured and is more clearly conveyed. A size of each component
does not correspond to its actual size. In addition, the
description is given using the same reference numerals for the same
components in the drawings throughout the specification.
Throughout the specification, a description that one part
"includes" one component means that the one part can further
include other components, rather than excluding other components
unless specifically stated to the contrary. Furthermore, the term
"or" in any of the detailed description or the claims is used not
to mean exclusive "or," but is intended to mean inclusive "or."
That is, unless otherwise specified or unless clear from the
context, a phrase "X uses A or B" is intended to mean any of
natural inclusive permutations. That is, the phrase "X uses A or B"
is met by both of the following examples: X uses A; X uses B; or X
uses both A and B. In addition, articles "a" and "an" used in this
application and the appended claims should generally be interpreted
to mean "one or more" unless otherwise specified or unless clear
from the context intending a singular form. Furthermore, terms such
as " . . . unit," " . . . instrument," and "module," described in
the specification mean a unit configured to process at least one
function or operation and can be embodied by hardware or software
or a combination of hardware and software.
Additionally, in the following description, a terminal apparatus is
a generic term of a movable or fixed user terminal instrument, such
as User Equipment (UE), mobile stations (Mobile Station (MS) and a
Mobile Terminal (MT)), a mobile station apparatus, a mobile
terminal, a subscriber unit, a subscriber station, a wireless
terminal, a mobile device, a node, a device, a remote station, a
remote terminal, a wireless communication device, a wireless
communication apparatus, a user agent, and an access terminal. The
terminal apparatus can be a cellular phone, a cordless phone, a
session initiation protocol (SIP) phone, a smartphone, a wireless
local loop (WLL) station, a personal digital assistant (PDA), a
tablet, a laptop, a hand-held communication device, a hand-held
computing device, a satellite radio, a wireless modem card, a
router, and/or another processing device for communications through
a wireless system. The base station apparatus is a generic term of
any given network-end node communicating with a terminal, such as a
node B (NodeB), an enhanced node B (eNodeB), a base station, and an
access point (AP). Note that the base station apparatus includes a
Remote Radio Head (RRH, a device including an outdoor radio unit
smaller than the base station apparatus, also referred to as a
Remote Radio Unit (RRU)) (also referred to as a remote antenna and
a distributed antenna). It can be said that the RRH is a special
configuration of the base station apparatus. It can be said that,
for example, the RRH is a base station apparatus in which only a
signal processing unit is included, and configuration of parameters
used in the RRH, determination of scheduling, and the like are
performed by another base station apparatus.
The terminal apparatus of the present invention may be configured
to include a memory and a processor. The memory stores instructions
related to various processes described below. The processor is
coupled to the memory and configured to perform the instructions
stored in the memory. The base station apparatus of the present
invention may be configured to include a memory and a processor.
The memory stores instructions related to various processes
described below. The processor is coupled to the memory and
configured to perform the instructions stored in the memory.
First Embodiment
FIG. 1 is one example of a radio communication system according to
the present embodiment. The system includes a base station
apparatus 101, a terminal apparatus 102, and a terminal apparatus
103. One or more antenna ports may be configured for each
apparatus. Here, the antenna port refers to a logical antenna that
can be recognized by an apparatus that performs communications,
rather than a physical antenna.
FIG. 2 is one example of a configuration of the terminal apparatus
according to the present embodiment. While the following gives the
description with an example in a case that information data (data
signal) is transmitted to the base station, a case that control
information, not the information data, is transmitted to the base
station is also included in one aspect of the present invention.
That is, one aspect of the present invention may be applied to, not
a Physical Uplink Shared Channel (PUSCH), but a Physical Uplink
Control Channel (PUCCH). In the present embodiment, the control
information transmitted from the base station apparatus 101 is
received by a control information reception unit 211 via a receive
antenna 210 in the terminal apparatus 102. The received control
information (configuration information of a higher layer (Radio
Resource Control (RRC)) or downlink control information (DCI)) is
input to a transmission parameter configuration unit 212. In the
parameter configuration, a coding rate, a modulation scheme, a
sparse code pattern for spreading, and radio resource allocation
information are configured. Information on the coding rate is input
to a coding unit 201, information on the modulation scheme is input
to a modulating unit 202, information on the sparse code pattern is
input to a spread unit 203, and information on the radio resource
allocation information is input to the coding unit 201 and the
mapping unit 204. Note that, the pieces of the information
described above need not be uniquely determined only with signals
input from the control information reception unit 211, and the
inputs from the control information reception unit 211 may allow
some candidates to be selected, and the terminal apparatus may
autonomously determine the transmission parameter. In addition, for
example, not only patterns in which allocations of zeros in the
sparse codes are different, but also multiple candidates of sparse
codes in which the number of zeroes (non-zeroes) are different may
be present, and according to a status of the terminal (for example,
a remaining amount of battery and a QoS), and the like, the
terminal apparatus may autonomously determine the sparse code. In
addition, regarding radio resources as well, some candidates that
have different bandwidths and include different numbers of OFDM
symbols (including the number of slots or subframes or frames) may
be present.
The transmission data is input to the coding unit 201, and an error
correcting code is applied. A turbo code, an LDPC code, a
convolutional code, a polar code, and the like are usable as the
error correcting code. A coded bit sequence output from the coding
unit 201 is input to the modulating unit 202. Modulation processing
such as BPSK, QPSK, 16QAM, 64QAM, 256QAM, and 1024QAM are performed
by the modulating unit 202. Note that, as described in NPL 3, the
processing in the spread unit 203 and the processing in the
modulating unit 202 may be performed collectively. A modulation
symbol sequence output by the modulating unit 202 is input to the
spread unit 203. The spread unit 203 spreads modulation symbols in
the input modulation symbol sequence.
FIG. 3 is an example of spreading the modulation symbols according
to the present embodiment. FIG. 3 illustrates an example of
spreading in a frequency domain. Each of the modulation symbols is
mapped to a resource element including one frequency domain
(subcarrier) and one time domain (OFDM symbol) as a unit of a radio
resource area. In the present embodiment, the radio resource area
to which the modulation symbol after the spreading is mapped
includes one or more frequency domains (subcarriers) and one or
more time domains (OFDM symbols). Note that although a subframe
configuration of the LTE is utilized and reference signals are
inserted into the 4th and 11th OFDM symbols, the positions and the
number of reference signals are not limited thereto, the reference
signal may be mapped to the head of the subframe (slot, mini-slot),
or the number of reference signals may be variable. For example, in
FIG. 3, the 1st modulation symbol is mapped to radio resources
including the 1st subcarrier to the 4th subcarrier in the 1st OFDM
symbol based on the sparse code. The 2nd modulation symbol is
mapped to radio resources including the 5th subcarrier to the 8th
subcarrier in the 1st OFDM symbol based on the sparse code. The 3rd
modulation symbol is mapped to radio resources including the 9th
subcarrier to the 12th subcarrier in the 1st OFDM symbol based on
the sparse code. FIG. 3 is an example in which the same sparse code
is used in the radio resource area including 12 subcarriers and 14
OFDM symbols. FIG. 3 illustrates an example in which the 1st
modulation symbol is spread to the 1st and 4th subcarriers
(resource elements) in the 1st OFDM symbol using a sparse code
[1,0,0,1], the 2nd modulation symbol is spread to the 5th and 8th
subcarriers in the 1st OFDM symbol using the sparse code [1,0,0,1],
and the 3rd modulation symbol is spread to the 9th and 12th
subcarriers in the 1st OFDM symbol using the sparse code [1,0,0,1].
However, the non-zero element is not limited to one but may be a
complex number with amplitude of 1. The amplitude may not be 1, but
may be a value of a certain power for all the sparse codes. FIG. 3
is a case in which the same spread pattern is applied to all OFDM
symbols. FIG. 4 is another example of spreading the modulation
symbols according to the present embodiment. As illustrated in FIG.
4, a different sparse code can be used for each OFDM symbol. For
example, in FIG. 4, the 1st modulation symbol is mapped to the
radio resources including the 1st subcarrier to the 4th subcarrier
in the 1st OFDM symbol based on the sparse code. The 2nd modulation
symbol is mapped to the radio resources including the 5th
subcarrier to the 8th subcarrier in the 1st OFDM symbol based on
the sparse code. The 3rd modulation symbols is mapped to the radio
resources including the 9th subcarrier to the 12th subcarrier in
the 1st OFDM symbol based on the sparse code. FIG. 4 illustrates an
example in which the 1st modulation symbol is spread to the 1st and
4th subcarriers in the 1st OFDM symbol using a sparse code
[1,0,0,1], the 2nd modulation symbol is spread to the 5th and 8th
subcarriers in the 1st OFDM symbol using a sparse code [0,0,1,1],
and the 3rd modulation symbol is spread to the 9th and 12th
subcarriers in the 1st OFDM symbol using a sparse code [1,0,1,0].
At this time, the sparse code to be used is determined by
information on a sequence index of the sparse code, a time index
such as a subframe number, and a frequency index such as a
subcarrier number, which are input from the transmission parameter
configuration unit 212.
As described above, in a case that a sequence length of the sparse
code is four and the number of null carriers in the sparse code
(the number of zero elements in the sparse code) is two, there are
.sub.4C.sub.2=six patterns of sequences of the sparse code. This is
one example, and in a case that the sequence length is configured
to be longer, the number of sequences increases. Here, the PAPR of
the OFDM symbol is dependent on the sequence. Accordingly, the
transmission parameter configuration unit 212 holds only sequences
of which the PAPR is smaller than a predetermined value, and
selects a code from limited sequences, thus making it possible to
prevent the PAPR from increasing.
As a method to prevent the PAPR from increasing, there is a method
of using only the sparse codes that cause the subcarriers to be
allocated at equal intervals. An output from the modulating unit
202 is not input to the spread unit 203, but is input to a DFT unit
(not illustrated) to apply a DFT. A signal after the DFT is input
to the spread unit 203. The spread unit 203 non-contiguously
allocates spectra at equal intervals, thus allowing sparse (sparse)
signals to be generated in the frequency domain or in the time
domain while preventing peak power from increasing. The intervals
of the spectra of the respective terminal apparatuses need not be
constant, and the base station apparatus notifies a position of the
first subcarrier and the interval of the spectra with the DCI or by
the RRC.
In a case that the sparse code is applied to the frequency domain,
performing scrambling processing is considered as another method
for preventing the PAPR from increasing. A scrambling unit is
inserted between the mapping unit 204 and an IFFT unit 205, and the
scrambling processing is applied to an output from the mapping unit
204. The scrambling processing is performed with a code, such as a
PN code and an M sequence. The sequence is not limited thereto, and
the input sequence may be multiplied by any sequence, such as a ZC
sequence. Note that the sequence to be used may be configured with
a cell-specific ID, a terminal-specific ID, or the like, and a
subframe number or the like.
Any reference signal may be used. Since the reference signals of
the multiple terminal apparatuses need to be separated, a cyclic
shift, an OCC, an Interleaved Frequency Division Multiple Access
(IFDMA), or the like needs to be used. Accordingly, for example,
associating an amount of turning of the cyclic shift and the like
with the sequence of sparse code allows the sequences of both of
the reference signal and the sparse code to be generated by
notifying one value from the base station apparatus to the terminal
apparatus. The number of cyclic shift values is designed to be the
same as or greater than the number of sequences of the sparse code.
Thus, in a case that the value of the cyclic shift is configured,
the sequence of sparse code is uniquely determined. Alternatively,
a control signal that specifies one sparse code among the multiple
sparse codes associated with the same cyclic shift may be received
to determine the sparse code. The reference signal is generated by
a reference signal generation unit (not illustrated) and is input
to the mapping unit 204.
FIG. 5 is another example of spreading the modulation symbols
according to the present embodiment. FIG. 5 illustrates an example
of spreading the SCMA in the time domain. FIG. 5 is an example in
which the same sparse code is used in the radio resource area
including the 12 subcarriers and the 14 OFDM symbols. In FIG. 5,
the 1st modulation symbol is mapped to radio resources (excluding
areas to which the reference signals are mapped) including the 1st
time domain (OFDM symbol) to the 5th time domain in the 1st
frequency domain (subcarrier) based on the sparse code. The 2nd
modulation symbol is mapped to radio resources including the 1st
time domain to the 5th time domain in the 2nd frequency domain
based on the sparse code. The 3rd modulation symbol is mapped to
radio resources including the 1st subcarrier to the 5th subcarrier
in the 3rd frequency domain based on the sparse code. Similarly,
other modulation symbols are mapped to the time domains based on
the sparse codes. FIG. 5 illustrates an example in which the 1st
modulation symbol are spread to the 1st and 5th OFDM symbols
(resource elements) in the 1st subcarrier using a sparse code
[1,0,0,1], the 2nd modulation symbol is spread to the 1st and 5th
OFDM symbols in the 2nd subcarrier using a sparse code [1,0,0,1],
and the 3rd modulation symbol is spread to the 1st and the 5th OFDM
symbols in the 3rd subcarrier using a sparse code [1,0,0,1]. For
this reason, while the 1st, 5th, 6th, 9th, 10th, and 14th OFDM
symbols have data in all subcarriers, the 2nd, 3rd, 7th, 8th, 12th,
and 13th OFDM symbols do not have data, and therefore the OFDM
symbols are not transmitted. As a result, in considering an entire
subframe, the average transmit power decreases compared to a case
that all the OFDM symbols have data. However, the peak does not
fall as much, and therefore the PAPR increases compared to a case
of the spreading in the frequency domain.
Therefore, use of a different sparse code for each subcarrier is
considered, rather than use of the same sparse code for the
respective subcarriers for spreading. FIG. 6 is another example of
spreading the modulation symbols according to the present
embodiment. FIG. 6 illustrates an example of spreading in the time
domain using a different sparse code for each subcarrier. For
example, in FIG. 6, the 1st modulation symbol mapped to the 1st to
5th OFDM symbols in the 1st subcarrier is spread with [1,0,0,1].
Thus, the data is duplicated (allocated) to the 1st and 4th OFDM
symbols (resource elements) in the 1st subcarrier. Similarly, the
2nd modulation symbol mapped to the 1st and 3rd OFDM symbols in the
2nd subcarrier is spread with [1,0,1,0]. Thus, the data is
duplicated to the 1st and 3rd OFDM symbols in the 2nd subcarrier.
Other modulation symbols are similarly spread. As a result, since a
subcarrier where data transmission is performed is present in all
OFDM symbols, an OFDM symbol of which the transmit power is zero is
less likely to be generated. Thus, significant degradation of the
PAPR can be avoided. Here, while the base station apparatus may
notify the terminal apparatus of which sparse code to be used to
spread each modulation symbol, the base station apparatus may
notify the terminal apparatus of only an index of a reference
sparse code such that the sparse codes applied to modulation
symbols are determined by the index of the sparse code, a
subcarrier index, and an OFDM symbol index. Here, the sparse code
index notified from the base station apparatus to the terminal
apparatus may be notified using the DCI or the RRC.
By spreading the data with the different sparse codes for the
subcarriers, the OFDM symbol where the number of subcarriers is
zero, that is, the transmit power is zero is less likely to occur,
making it possible to improve the PAPR.
The description that the PAPR can be improved by using a different
sparse code for each subcarrier in a case that the sparse codes are
applied in the time direction has been given by using FIG. 6.
However, for example, while the 1st OFDM symbol includes seven
subcarriers in FIG. 6, the 2nd OFDM symbol includes five
subcarriers. In other words, in a case that a spectral power
spectral density is constant in the subcarriers, the power of the
2nd OFDM symbol is comparatively low, and the power of the 1st OFDM
symbol is comparatively high. This means that the transmit power is
different for each OFDM symbol. This also causes the degradation of
the PAPR. Next, a method for selecting sparse codes to solve the
problem will be described.
FIG. 7 is another example of spreading the modulation symbols
according to the present embodiment. FIG. 7 illustrates an
application example of the sparse codes in a case that the transmit
power of each OFDM symbol is constant. FIG. 7 illustrates an
example of spreading in the time domain using a different sparse
code for each subcarrier. In FIG. 7, the sparse codes are applied
such that the number of subcarriers becomes six in each OFDM
symbol. As a result, since the transmit power does not change for
each OFDM symbol, the deterioration of the PAPR is less likely to
occur. There are various methods to cause the numbers of
subcarriers in the respective OFDM symbols to be constant. As an
example, the sparse codes used in the respective subcarriers are
configured to be the same and all of the sparse codes are used by
the same number of times in frequency resources allocated. As a
result, the numbers of null subcarriers in the respective OFDM
symbols become constant, and therefore the deterioration of the
PAPR can be reduced.
FIG. 10 is another example of a method for causing the numbers of
subcarriers in the respective OFDM symbols to be constant. As
illustrated in FIG. 10, also in a case that the same sparse codes
are applied in the time direction, using the sparse codes in a
temporally cyclic manner allows the numbers of subcarriers in the
respective OFDM symbols to be constant.
The output from the spread unit 203 is input to a mapping unit 204.
The mapping unit 204 uses the input from the spread unit 203 and
the reference signal input from the reference signal generation
unit to generate a frame (subframe, slot, or mini-slot). The output
from the mapping unit 204 is input to the IFFT unit 205, and IFFT
processing is applied. A signal after the IFFT is applied is input
to a CP addition unit 206. The CP addition unit 206 adds a Cyclic
Prefix (CP). A signal to which the CP is added is input to a radio
transmitting unit 207. In the radio transmitting unit 207,
filtering processing and up-conversion are applied. A signal output
from the radio transmitting unit 207 is transmitted to the base
station apparatus via a transmit antenna 208.
FIG. 8 illustrates a configuration example of the base station
apparatus. A signal transmitted by the terminal apparatus is
received by a radio receiving unit 802 via a receive antenna 801.
The radio receiving unit 802 applies the filtering processing and
the up-conversion processing. The output from the radio receiving
unit 802 is input to a CP removal unit 803. The CP removal unit 803
removes the CP added by the terminal apparatus. The output from the
CP removal unit is input to an FFT unit 804. The FFT unit 804
converts a time domain signal into a frequency domain signal. The
output from the FFT unit 804 is input to a de-mapping unit 805. The
de-mapping unit 805 demultiplexes the reference signal multiplexed
by the terminal apparatus and extracts resources used for the
communications. The output from the de-mapping unit 805 is input to
a signal separator 806. The signal separator 806 applies the
filtering processing, cancelling processing, Belief Propagation
(BP), MPA, maximum likelihood estimation, and the like to
demultiplex the signals transmitted by the respective transmission
apparatuses. The signal output from the signal separator 806 is
input to a despread unit 807. The despread unit 807 performs
despread processing with a spreading code sequence input from a
transmission parameter storage unit 813. The sparse code sequence
is determined from information included in the control information
input from a control information configuration unit 812, a
subcarrier index, a subframe index, an OFDM symbol index, or the
like. Note that while the signal separator 806 and the despread
unit 807 are configured as separate blocks in the present
embodiment, the signal separation and the despread may be performed
in the same block. The output from the despread unit 807 is input
to a demodulation unit 808. The demodulation unit 808 is notified
of a modulation scheme applied in the transmission apparatus from
the transmission parameter storage unit 813, demodulation
processing is applied based on the modulation scheme, and a bit Log
Likelihood Ratio (LLR) sequence is output. The output from the
demodulation unit 808 is input to a decoding unit 808. Information
on error correcting coding, such as a coding rate, input from the
transmission parameter storage unit 813 is input to a decoding unit
810, and information bits after the error correction are obtained
from the information and the bit LLR sequence input from the
demodulation unit 808. Note that at least a part of the information
input to the transmission parameter storage unit 813 by the control
information configuration unit 812 is input to the terminal
apparatus via a transmit antenna 811.
As described above, in a case that the SCMA is applied, the SCMA
spreading code is changed for each OFDM symbol and/or for each
subcarrier, thus allowing a tolerance to a channel variation to be
improved and allowing the PAPR to be improved.
Second Embodiment
While the example where the sparse codes are applied to the
multiple OFDM symbols in one subframe has been described in the
first embodiment, an example where different sparse codes are used
in different subframes (slots, mini-slots) will be described in the
present embodiment.
For example, in FIG. 3, in a case that degradation due to frequency
selective fading occurs in the frequency indexes 8 and 9, an error
occurs. Accordingly, the base station apparatus transmits the
control information to the terminal apparatus such that the
different sparse codes are used during retransmission. For example,
FIG. 9 illustrates an example of selecting the sparse codes for
using the subcarriers not used with the sparse codes used in FIG.
3. In the example, since the frequency indexes 8 and 9 are not
used, in a case that a channel (channel) has a gradual time
variation, the control information reception unit 211 in the
terminal apparatus receives the information on the sparse code for
retransmission and inputs the information to the transmission
parameter configuration unit 212. Note that FIG. 9 is one example,
and the same subcarrier as the subcarrier used in the initial
transmission or the previous transmission may be used. Based on the
information on the sparse code for retransmission, the parameter
configuration unit 212 inputs a sequence of the sparse code
different from that of the initial transmission to the spread unit
203. Note that it is not always necessary to notify the information
on the sparse code from the base station apparatus at the time of a
retransmission request, and a sparse code may be determined by the
information on the sequence of the sparse code notified at the time
of the initial transmission and the number of retransmissions
(redundancy version). Furthermore, the terminal apparatus may
autonomously select a sparse code from multiple sparse codes.
During retransmission, a sequence length of the sparse code,
namely, a spreading rate, may be changed for transmission.
Information on the spreading rate may be included in the DCI
notified from the base station, or may be defined by the RRC.
In this manner, the use of the sparse code different from that of
the initial transmission at the time of the retransmission allows
the transmission to be performed using at least partially different
subcarriers and/or OFDM symbols, making it possible to obtain
satisfactory transmission performance due to frequency and/or time
diversity.
A program running on an apparatus according to one aspect of the
present invention may serve as a program that controls a Central
Processing Unit (CPU) and the like to cause a computer to operate
in such a manner as to realize the functions of the above-described
embodiments according to the present invention. Programs or the
information handled by the programs are temporarily read into a
volatile memory, such as a Random Access Memory (RAM) while being
processed, or stored in a non-volatile memory, such as a flash
memory, or a Hard Disk Drive (HDD), and then read by the CPU to be
modified or rewritten, as necessary.
Moreover, the apparatuses in the above-described embodiment may be
partially enabled by a computer. In that case, a program for
realizing the functions of the embodiments may be recorded on a
computer readable recording medium. This configuration may be
realized by causing a computer system to read the program recorded
on the recording medium for execution. It is assumed that the
"computer system" refers to a computer system built into the
apparatuses, and the computer system includes an operating system
and hardware components such as a peripheral device. Furthermore,
the "computer-readable recording medium" may be any of a
semiconductor recording medium, an optical recording medium, a
magnetic recording medium, and the like.
Moreover, the "computer-readable recording medium" may include a
medium that dynamically retains a program for a short period of
time, such as a communication line that is used for transmission of
the program over a network such as the Internet or over a
communication line such as a telephone line, and may also include a
medium that retains a program for a fixed period of time, such as a
volatile memory within the computer system for functioning as a
server or a client in such a case. Furthermore, the program may be
configured to realize some of the functions described above, and
also may be configured to be capable of realizing the functions
described above in combination with a program already recorded in
the computer system.
Furthermore, each functional block or various characteristics of
the apparatuses used in the above-described embodiments may be
implemented or performed on an electric circuit, that is, typically
an integrated circuit or multiple integrated circuits. An electric
circuit designed to perform the functions described in the present
specification may include a general-purpose processor, a Digital
Signal Processor (DSP), an Application Specific Integrated Circuit
(ASIC), a Field Programmable Gate Array (FPGA), or other
programmable logic devices, discrete gates or transistor logic,
discrete hardware components, or a combination thereof. The
general-purpose processor may be a microprocessor or may be a
processor of known type, a controller, a micro-controller, or a
state machine instead. The above-mentioned electric circuit may
include a digital circuit, or may include an analog circuit.
Furthermore, in a case that with advances in semiconductor
technology, a circuit integration technology appears that replaces
the present integrated circuits, it is also possible to use an
integrated circuit based on the technology.
Note that the invention of the present patent application is not
limited to the above-described embodiments. In the embodiment,
apparatuses have been described as an example, but the invention of
the present application is not limited to these apparatuses, and is
applicable to a terminal apparatus or a communication apparatus of
a fixed-type or a stationary-type electronic apparatus installed
indoors or outdoors, for example, an AV apparatus, a kitchen
apparatus, a cleaning or washing machine, an air-conditioning
apparatus, office equipment, a vending machine, and other household
apparatuses.
The embodiments of the present invention have been described in
detail above referring to the drawings, but the specific
configuration is not limited to the embodiments and includes, for
example, an amendment to a design that falls within the scope that
does not depart from the gist of the present invention.
Furthermore, various modifications are possible within the scope of
one aspect of the present invention defined by claims, and
embodiments that are made by suitably combining technical means
disclosed according to the different embodiments are also included
in the technical scope of the present invention. Furthermore, a
configuration in which components, described in the respective
embodiments and having mutually the same effects, are substituted
for one another is also included in the technical scope of the
present invention.
The embodiments of the present invention have been described in
detail above referring to the drawings, but the specific
configuration is not limited to the embodiments and includes, for
example, an amendment to a design that falls within the scope that
does not depart from the gist of the present invention.
Furthermore, various modifications are possible within the scope of
one aspect of the present invention defined by claims, and
embodiments that are made by suitably combining technical means
disclosed according to the different embodiments are also included
in the technical scope of the present invention. Furthermore, a
configuration in which components, described in the respective
embodiments and having mutually the same effects, are substituted
for one another is also included in the technical scope of the
present invention.
INDUSTRIAL APPLICABILITY
One aspect of the present invention can be used, for example, in a
communication system, communication equipment (for example, a
cellular phone apparatus, a base station apparatus, a wireless LAN
apparatus, or a sensor device), an integrated circuit (for example,
a communication chip), or a program.
REFERENCE SIGNS LIST
101 Base station apparatus 102, 103 Terminal apparatus 201 Coding
unit 202 Modulating unit 203 Spread unit 204 Mapping unit 205 IFFT
unit 206 CP addition unit 207 Radio transmitting unit 208 Transmit
antenna 210 Receive antenna 211 Control information reception unit
212 Transmission parameter configuration unit 801 Receive antenna
802 Radio receiving unit 803 CP removal unit 804 FFT Unit 805
De-mapping unit 806 Signal separator 807 Despread unit 808
Demodulation unit 810 Decoding unit 811 Transmit antenna 812
Control information configuration unit 813 Transmission parameter
storage unit
* * * * *